The present invention relates generally to a clamp and more specifically to a fluid powered, locking pin clamp.
Automated or powered clamps have been commonly used to secure workpieces, such as sheet metal automotive vehicle body panels, polymeric parts and the like in checking fixtures, gauging stations, welding stations and punching machines. Many existing clamps are powered by hydraulic or pneumatic fluid pressure. For example, reference should be made to the following U.S. Patents, which have been invented by Sawdon: U. S. Pat. No. 5,884,903 entitled xe2x80x9cPowered Clamp Gauging Apparatusxe2x80x9d which issued on Mar. 23, 1999; U.S. Pat. No. 5,165,670 entitled xe2x80x9cRetracting Power Clampxe2x80x9d which issued on Nov. 24, 1992; and U.S. Pat. No. 5,190,334 entitled xe2x80x9cPowered Clamp with Parallel Jawsxe2x80x9d which issued on Mar. 2, 1993; all of which are incorporated by reference herein.
It has recently become desirable to prevent a gripping arm from opening and releasing the workpiece if there is a loss of fluid pressure. Gripper constructions employing such a feature are disclosed in U.S. Pat. No. 5,871,250 entitled xe2x80x9cSealed Straight Line Gripperxe2x80x9d which issued to Sawdon on Feb. 16, 1999, and U.S. Pat. No. 5,853,211 entitled xe2x80x9cUniversal Gripperxe2x80x9d which issued to Sawdon et al. on Dec. 29, 1998. These patents are also incorporated by reference herein.
In accordance with the present invention, a preferred embodiment of a clamp employs a workpiece-clamping member, a clamp body, and a driving member. In another aspect of the present invention, a fluid actuated piston is operable to drive a clamping member. A further aspect of the present invention provides a camming mechanism to couple a clamping member to a camming member. Still another aspect of the present invention employs a piston and a clamping member wherein the piston advances in a direction generally perpendicular to a direction of movement of the clamping member. A detent arrangement is provided on a camming surface in yet another aspect of the present invention, in order to deter inadvertent unclamping of a workpiece if the desired fluid pressure is not present. Another aspect of the present invention, allows a clamping member to retract into a hollow locating pin extending from a clamp body. A method of operating a clamp is also provided.
The locking pin clamp of the present invention is highly advantageous over traditional clamps in that the moving clamping member of the present invention can be maintained in its clamping position even during loss of piston fluid pressure. This eliminates undesired opening of the clamping member which can lead to inadvertent dropping and damage of the workpiece. The present invention is also advantageous in that the clamping member can be retracted into a locating pin whereby the workpiece can first be located relative to the clamp body and then clamped against the clamp body, in a single, compact and multi-functional package; thus, the clamping member does not need to be remotely located away from the target locating pin. Furthermore, the present invention allows for four point equidistant locating or gauging against the workpiece even when openings are provided in the locating pin for passage of the clamping member. This four point locating and contacting against the workpiece provides accurate workpiece-to-pin alignment that coincides with the typically designed geometric tolerancing and dimensioning characteristics of the workpiece.
The specific perpendicular orientation of the piston movement relative to the general direction of clamping member movement advantageously encourages locking of the clamping member in the clamping position if fluid pressure is not present. Moreover, this generally perpendicular arrangement is resistant to being back driven and is further maintained in the clamping position by use of a set of detent formations located along a camming surface. Another advantage of the present invention is the ability to rotate one or more piston cylinders 360 degrees relative to the body even after the piston cylinder is fully installed in the body. This allows for convenient routing of fluid carrying tubes and fittings to the piston cylinders free of adjacent obstructions in the manufacturing facility. Additional advantages and features of the present invention will become apparent from the following description and appended claims, taken in conjunction with the accompanying drawings.